1. Field of the Invention
The present invention relates to a pattern forming method and pattern forming apparatus for forming a predetermined resist pattern in, e.g., manufacturing semiconductor devices, wherein light exposure is performed on a resist film in accordance with a predetermined pattern by immersion light exposure, and then development of a light exposure pattern is performed.
2. Description of the Related Art
In a photolithography step for semiconductor devices, resist is applied onto a semiconductor wafer (which will be simply referred to as “wafer”) to form a resist film, which is subsequently subjected to light exposure in accordance with a predetermined circuit pattern, and a development process to form a circuit pattern on the resist film.
According to the most advanced photolithography step of this kind, it is possible to form a minute circuit pattern with a line width of about 90 nm (a 90-nm node level).
In recent years, circuit patterns of semiconductor devices have been increasingly smaller, and technical development is further proceeding from the 90-nm node level toward a 45-nm node level. Along with this trend, it is required to improve characteristics of light exposure concerning the resolution performance. Accordingly, a light exposure technique using extreme ultraviolet light (EUVL: Extreme Ultra Violet Lithography), a light exposure technique using dimeric fluorine (F2), and so forth have been developed. Further, for example, on the basis of an improvement to enhance the resolution performance in a light exposure technique using argon fluoride (ArF) or krypton fluoride (KrF), there has been proposed a method for performing light exposure while providing a liquid layer consisting of light-transmitting liquid on the surface of a substrate (which will be referred to as “immersion light exposure”), (for example, see International Publication No. WO 99/49504).
Further, as regards the immersion light exposure, in order to prevent the light-transmitting liquid (which will be referred to as “immersion liquid”) from coming into direct contact with the resist film during light exposure, there has been proposed a method for performing immersion light exposure from above a protection film (which will be referred to as “top coating”), which is formed on the resist film in advance (see Jpn. Pat. Appln. KOKAI Publication No. 2005-157259).
On the other hand, in order to omit the step of forming the protection film, there has been studied a method for performing immersion light exposure directly on the surface of the resist film without using the top coating, i.e., in a top coating-less manner.
In any of the methods described above, the surface of the top coating or resist film needs to be hydrophobic, so that a sufficient liquid resistance is ensured against the immersion liquid during the light exposure, and the immersion head of the light exposure unit can be moved at a sufficient scanning speed.
Where a development process is performed on a wafer having a top coating or resist film formed thereon with a hydrophobic surface, the wafer surface repels the development liquid applied thereon, and thereby hinders the development liquid from being filled on the wafer. In this case, it is difficult to perform development uniformly and reliably on the wafer, resulting in fluctuations in CD (Critical Dimension) and faults of the development process, such as generation of defects. Consequently, a problem arises such that a predetermined resist pattern cannot be uniformly and reliably formed.